行星际磁重联与湍流关系研究

The relation between magnetic reconnection and turbulence is an important and frontier topic in space physics. It is much more important in the interplanetary space since the solar wind is full of turbulences. Up to now, there is a lot of work have been done by the scholars on the subjects of interplanetary magnetic reconnection and turbulence, and these research mainly aim on the large-scale, qusi-steady reconnection exhausts and the properties of the turbulence themselves. Compared with these work, there are relatively less research on the relations between interplanetary magnetic reconnection and turbulence. In addition, due to the lack of sufficient and detailed observations with high-resolution data, there are still many questions should be discussed and analyzed. This project plans to analyse high-resolution data by the international collaborative research, discuss the turbulent properties on the inertial and dissipation range through the power spectrum density, structure properties and anisotropy, analyze the full spectrum behavior of the waves, particles and field, research the relations between interplanetary magnetic reconnection and turbulence by the aid of the numerical simulations, thus explain the relations between interplanetary magnetic reconnection and turbulence systematicly and deeply, and enhance the understanding of the nature of a basic physical process-the magnetic energy dissipation.

磁重联与湍流的关系研究是磁重联现象研究的一个重要前沿科学问题。特别是对于行星际太阳风这样一种极度湍动的介质而言，研究磁重联与湍流的关系尤为重要。到目前为止，国内外众多学者对大尺度准稳态的行星际磁重联和行星际湍流自身的特性做了大量的研究工作。研究行星际磁重联与湍流之间关系的工作则相对较少。加之由于缺乏足够而详尽的高分辨率观测事例分析，还有很多问题需要深入的讨论和分析。本项目计划通过国际合作研究，获取高精度的卫星数据，以当代湍流理论为指导，从磁场功率谱、结构属性、各向异性等方面入手，同时在惯性区和耗散区对比研究行星际磁重联的湍流特性，分析波、粒子和场的全谱行为，并借助数值模拟考察湍流与磁重联的关系，从而比较系统、深入的挖掘行星际空间湍流和磁重联的关系，增进对磁场耗散这一基本物理过程本质的认识。

湍流被认为是经典物理中最后一个没有解决的问题。太阳风湍流更复杂，它的无碰撞特性使得它与经典湍流的能量耗散过程完全不同，人们对飞船观测到的太阳风湍流进行了一系列的研究，但诸多观测结果以及耗散理论都存在着不一致性。在经历了长达几十年的争论以后，人们在2013年发起并成立了Turbulent Dissipation Challenge，各种太阳风湍流的耗散机制被大体上归为两类：一类是通过波粒相互作用耗散，另一类则是通过电流片，磁重联等过程耗散。到底太阳风湍流是通过哪种能量耗散机制被耗散的？时至今日，这个问题依然没有答案。此项目通过一系列研究首次发现了行星际磁重联产生的湍流在能量耗散区具有独特的多分形特性，这种特性又仅仅存在于在磁重联扩散区附近，与背景太阳风湍流的单分形湍动特性有着明显的区别。这些结果还表明磁重联耗散过程与背景太阳风湍流耗散过程中磁场的间歇性，标度系数，各向异性等均有不同。相关结果也得到了Turbulent dissipation challenge 第一召集人T. Parashar博士的高度评价，他说他们刚做出类似的工作就发现我们的论文已经发表了，他自述已跟踪研究这个方向很久了，而我们则首次在该方向做出了成果（We were very recently discussing that this should be done at some point and then I saw your paper…We had suspected it for a long time and your paper is first one along that direction）。..为什么磁重联附近区域的耗散是多分形的而背景太阳风耗散是单分形的？磁重联附近区域的间歇结构对湍流能量耗散又有什么影响？此项目也利用高分辨率，低数值粘性的数值模拟程序来解释相关的问题。设计数值模拟程序让重联自发产生湍流（而不是外部驱动湍流），分析耗散区湍动特性，初步结果显示Hall效应对耗散分形的影响。